This invention relates to an agricultural sprayer and more particularly to an apparatus for injecting pesticide, fungicides, and fertilizers into an airstream to spray foliage.
Agricultural spraying devices typically include a fan that generates a high speed air flow that is directed through a cowling at foliage. Pesticide is then directly fed through a nozzle into the air flow to spray the foliage. A few of these techniques are described in U.S. Pat. Nos. 4,347,978 and 4,768,713.
One of these techniques, described in U.S. Pat. No. 4,347,978, directs air from within a cowling and between rectangular-shaped paddles at foliage. The paddles then oscillate about a vertical axis and create turbulence in the air flow to shake leaves on the foliage. This shaking of the leaves improves pesticide coverage. However, this technique does not uniformly shake all the leaves. Further, the air turbulence created by this technique may result in some leaves covering up other leaves. Consequently, the covered leaves may not get sprayed. Further, in this technique the paddles are vertically spaced apart with air gaps between the paddles. Thus, portions of the air pass over the paddles without any direction and without any turbulence being generated.
It is desirable to simultaneously spray foliage by blowing air on both sides of the agricultural sprayer. One method to simultaneously spray two sides is to blow air on both sides of the sprayer with two fans. One blows air on one side of the sprayer and the other fan blows air on the other side. Pesticide is then injected into the air flow. Using two fans is inefficient as two motors and fan housings are needed. The inefficiency of two fans may be increased if the fans are stacked because the air from one fan may interfere with the air from the other fan.
Another method used to simultaneously spray two sides of the sprayer is by blowing air across a divider that directs the air at the foliage. Using a divider is inefficient as the divider creates a drag on the air flow. Further, the divider is undesirable as it adds weight and bulk to the agricultural sprayer.
Pesticide spray is typically injected into the air flow by locating a nozzle within the air flow itself. Liquid pesticide is fed through the nozzle into the air flow resulting in the pesticide particles being carried by the air onto the foliage. A drawback to this injection technique is that the size of the particles are not regulated. Consequently, a greater or lesser amount of pesticide may be applied than needed. When the pesticide is applied it may not be evenly dispersed resulting in too high of a concentration in one location and too low of a concentration in another location. Accordingly, some of the pesticide is wasted on portions of the foliage while other portions will have insufficient pesticide to protect the foliage from insects.
Sprayed pesticide is charged to increase its adherence to foliage. Methods of charging the pesticide are disclosed in U.S. Pat. Nos. 4,762,274, 4,565,318 and U.K. Patent Application 2 181 974 A. These methods involve first directing an air flow at the foliage to be sprayed. Second, a high-voltage electrostatic charge is placed on an electrode. Pesticide is injected into the air flow, and the air flow is passed over the electrode to charge the pesticide. A drawback to these methods is that a sprayer operator may be exposed to the high voltage causing a safety hazard. Further, pesticide may not flow into areas of close enough proximity to the electrode to become charged. Thus, maximum pesticide adherence to foliage may not be obtained.
Techniques for controlling the particle distribution of pesticide are disclosed in U.S. Pat. Nos. 4,768,713 and 4,823,268. These techniques involve using many ultrasonic sensors stacked vertically above each other in a fixed position. The sensors transmit an ultrasonic signal to detect the foliage in a zone. Nozzles associated with each sensor are vertically stacked and placed in an airstream exiting from the side of the sprayer. Each nozzle sprays into a particular zone and is associated with a sensor sensing that zone. The detector associated with the nozzle is used to turn different nozzles off and on depending on whether foliage is detected in the nozzle's zone. This technique uses many sensors. When a sensor breaks down they are expensive to replace. Further, the more sensors used, the more likely the probability of a failure, thus reducing the reliability of the sprayer.
The pesticide being injected in the nozzle is typically a mixture of water and pesticide. Methods of mixing the water and pesticide are described in U.S. Pat. Nos. 4,023,020, 4,803,626 and 4,805,086. These methods use industrial pumps to move water and pesticide into an injection line, However, if a water pump were to fail, pressure caused by the industrial pump could cause the pesticide to flow backwards into the water. This backflow results in the water being contaminated which is highly undesirable.